The present invention relates to network interfacing, and more particularly, to methods and systems for adaptively controlling the gain of an energy detector in a physical layer transceiver for data communications over existing residential telephone line wiring.
Local area networks use a network cable or other media to link stations on the network. Each local area network architecture uses a media access control (MAC) enabling network interface cards at each station to share access to the media.
Conventional local area network architectures use media access controllers operating according to half-duplex or full duplex Ethernet (ANSI/IEEE standard 802.3) protocol using a prescribed network medium, such as 10 BASE-T. Newer operating systems require that a network station to be able to detect the presence of the network. In an Ethernet10 BASE-T environment, the network is detected by the transmission of a link pulse by the physical layer (PHY) transceiver. The periodic link pulse on the 10 BASE-T media is detected by a PHY receiver, which determines the presence of another network station transmitting on the network medium based on detection of the periodic link pulses. Hence, a PHY transceiver at Station A is able to detect the presence of Station B, without the transmission or reception of data packets, by the reception of link pulses on the 10 BASE-T medium from the PHY transmitter at Station B.
Efforts are underway to develop an architecture that enables computers to be linked together using conventional twisted pair telephone lines instead of established local area network media such as 10 BASE-T. Such an arrangement, referred to herein as a home telephone wire network environment, provides the advantage that existing telephone wiring in a home may be used to implement a home network environment. However, telephone lines are inherently noisy due to spurious noise caused by electrical devices in the home, for example dimmer switches, transformers of home appliances, etc. In addition, the twisted pair telephone lines suffer from turn-on transients due to on-hook and off-hook and noise pulses from the standard Plain Old Telephone System (POTS) telephones, and electrical systems such as heating and air conditioning systems, etc.
An additional problem in telephone wiring networks is that the signal condition (i.e., shape) of a transmitted waveform depends largely on the wiring topology. Numerous branch connections in the twisted pair telephone line medium, as well as the different associated lengths of the branch connections, may cause multiple signal reflections on a transmitted network signal. Telephone wiring topology may cause the network signal from one network station to have a peak-to-peak voltage on the order of 10 to 20 millivolts, whereas network signals from another network station may have a value on the order of one to two volts. Hence, the amplitude and shape of a received pulse may be so distorted that recovery of transmit data from the received pulse becomes substantially difficult.
Accordingly, it would be desirable to provide a physical layer transceiver capable of adaptively controlling characteristics of its reception circuitry in a home network environment to optimize processing of received pulses.
The present invention provides a novel network station for receiving data transmitted via residential wiring. The network station comprises an input circuit for receiving an incoming pulse signal, and an energy detector responsive to the incoming pulse signal for producing a pulse energy value representing energy of the incoming pulse signal. An adaptive energy detector gain control circuit is responsive to the pulse energy value for adaptively controlling the gain of the energy detector so as to maintain the pulse energy value at a predetermined level.
In accordance with a preferred embodiment of the invention, each packet received by the input circuit comprises a plurality of access identification pulses preceding data pulses to identify a transmitting network station. The adaptive energy detector gain control circuit is configured to control the gain of the energy detector in response to at least one of the access identification pulses.
Preferably, the adaptive energy detector gain control circuit may comprise a comparator for comparing a pulse energy value produced by the energy detector with a preset threshold level, and a controller for supplying the energy detector with a gain control value. In response to the output of the comparator, the controller reduces the gain of the energy detector if the pulse energy value exceeds the threshold level, and raises the gain of the energy detector if the pulse energy value is less than the threshold level.
For example, the energy detector may comprise an integrator for performing integration over time. The energy detector gain control circuit may be configured to adjust a value of an integrated signal produced by the integrator.
In accordance with a method of the present invention, the following steps are carried out for receiving data transmitted via residential wiring:
producing by an energy detector a pulse energy value representing energy of an incoming pulse signal, and
adaptively controlling gain of the energy detector so as to maintain the pulse energy value at a predetermined level.
Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein only the preferred embodiment of the invention is shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.